1. Field of the Invention
The present invention relates to a multimedia storage and communication device and its judgment method and, more particularly, relates to a multimedia storage and communication device that can change its operation mode to a suitable signal interface mode so as to control the transmission rate and power consumption of the multimedia storage and communication device according to the control signal received from a host system.
2. Description of the Related Art
In general, there are many interfaces existing between small size memory card and host or portable electrical device, for example the CFC (Compact Flash Card) or SD (Secure Digital Card)/MMC (Multi-Media Card) are the popular two of them. However, the new generation memory cards with USB interface have the advantage of high transmission rate, such as the Express card designed by Intel cooperation and Intelligent Stick system designed by PQI®. The traditional intelligent Stick is a memory card with USB interface, and the USB 2.0 version interface has a transmission rate up to 60 Mbytes/second, however, it consumes more power than USB 1.1 version interface. Due to not every portable electronic device needs such high transmission rate, such as MP3 player. The traditional Intelligent Stick system only has USB 2.0 interface, which comprises VBUS, D−, D+ and GND terminals and has 5.0V operation voltage, a set of differential signals consisted of D−, D+ and a transmission rate up to 60 Mbytes/second. Due to the traditional Intelligent Stick system with USB 2.0 interface has higher transmission rate and consumes more power, therefore, it is suitable applied to an application required mass transmission data, for example but not limited to high resolution digital camera or digital video recorder.
The MMC (Multi-Media Card, referred as MMC card hereinafter) is a protocol defined by MMC association, which is a low cost data storage and communication device designed for smart phone, digital camera, personal digital assistant, digital video recorder, MP3 player or electronic games. The MMC card comprises 7 pins (remarks: wherein a pin is reserved) and its currently version is version 4.0. The MMC version 3.2 and its former version have a 3.3V or 1.8V operation voltage, 1 bit data width with synchronous clock and 0-20 MHz or 26 MHz operation frequency. However, for increasing the transmission rate, the MMC version 4.0 increases the data width to 1 bit, 2 bits, 4 bits and 8 bits, 0-20 MHz, 26 MHz or 52 MHz operation frequency and a transmission rate up to 52 Mbytes/Second so that its pins is increased to 13. Thought the MMC version 4.0 has a transmission rate up to 52 Mbytes/Second, it is still slower than the USB 2.0 with 60 Mbytes/Second but consumes less power. Due to the MMC version 4.0 has lower transmission rate and consumes less power, therefore, it is suitable applied to an application required less transmission data, for example but not limited to MP3 player, the third generation mobile phone, which requires less transmission data and long standby time features.
For the general memory cards, most of their interfaces only has one signal type, such as the multimedia card just has an MMC interface with synchronized signal, the Intelligent Stick 2.0 just has one USB interface with differential signal, although they can be applied to portable electronic device for digital image or MP3 audio signals transmitting, however, using the USB interface with the higher transmission rate and more power consumption to transmit the MP3 signal is not a good design in power saving; or using the MMC interface with the lower transmission rate and less power consumption to transmit the video signal, though it saves power but loses video quality. Therefore, the user must make a decision when he (or she) buys the multimedia card with MMC interface or memory card with USB interface.
Therefore, we need a memory storage device that is compatible to the existing system and has suitable transmission rate and power consumption to overcome the aforesaid drawbacks.